Many people celebrated Valentine's Day yesterday, and my wife and I spent the evening doing indoor rock climbing and having a meal at a restaurant. Over the years, I have found that spending time together doing things you both enjoy is so important. Building the relationship every day cements your friendship more than giving flowers and candy once in a while.
Furthermore, if you view relations only as a contract (you give 50% and I give 50%), then problems and unhappiness are bound to happen. Instead, try giving 100% of your effort to the other person. Now, there will be times in a life when unexpected situations arise that put pressure on a relationship (illness, death, financial strain), but when you accept first that life isn't always fair and that you really have to keep putting wood on the fire of love, then you are devoting all of your energies to make things work.
Here is one of my listening activities from my Web site, www.esl-lab.com, on what NOT to do to maintain love in a relationshop.